Driving mechanism for x-ray grids



April 19, 1949.

R. H. MORGAN ET AL DRIVING MECHANISM FOR X-RAY GRIDS w WN WW a 6 w v Md n m Sm: n 0 NM eflfi m Ma a Q fix! MM; QM;

Filed July 22, 1943 April 19, 1949i 7 R. H. MORGAN ET AL 2,467,592

DRIVING MECHANISM FOR X-RAY GRI DS Filed July 22, 1943 2 Sheets-Sheet 2 FIE 3 Patented Apr. 19, 1949 lJNlTED STATES DRIVING MECHANISM FOR. X-BAY GRIDS.

Application July 22; 1943, Serial No. 495,690

2 Glaims; 1

This invention relates to an X-ray apparatus and more particularly to a driving mechanism for imparting reciprocating movements to a socalled Potter-Bucky grid.

In taking certain X-ray photographs it is a common practice touse a moving grid called a Bucky grid or Bucky diaphragm between the source of X-rays and the film. In order to secure a properly exposed film without grid lines it is essential that the Bucky diaphragm be moved at a uniform speed and that reversal of its movement be substantially instantaneous.

It is. thus an object of the present invention to provide a driving mechanism for a Bucky grid or diaphragm that will substantially instantaneous.- ly reverse the direction of movement, of the. grid, in its reciprocation.

It is another and still further object of the. present invention to provide a mechanism of the character stated wherein. the arms of an oscillatable fork are adapted for alternate engagement respectively with oppositely threaded portions of a positively driven member for effecting a substantially instantaneous reversal of the direction of movement of the Bucky diaphragm.

These and other objects will be apparent from the following detailed description of av preferred embodiment of the invention taken in connection with the accompanying drawings in which:

Fig. 1 is a partly sectioned elevational View of the driving mechanism; Fig. 2 is a sectional view taken vertically on the line 2.--2= of Fig. 1; and Fig. 3 is an elevational view of. the driving mechanism coupled to a Potter-Bucky grid in operative relation to an X-ray tube. Fig. 4 is a section taken on the line 44 of Fig. 1.

With reference to Fig. 1, a constant speed electric driving motor and a reciprocating mechanism 2| are mounted on a base 22. The motor 20 supported by a resilient mounting 23 rotates through a flexible coupling 24, a member 25, which is supported in brackets 26 and 21 and is provided with left-hand and right-hand threaded portions. Thus a portion 25a of member 25 is threaded in one direction while a similar portion 25b is threaded in the opposite direction. In the brackets 26 and 21 above the member 25 is a parallel guide rod 28 on which a forked member 29 reciprocates and oscillates. This member 29 comprises a forked body 30 drilled axially to receive the rod 28 and formed to provide two arms 32 and 33 which extend downwardly, one on either side of the rotating member 25. As best illustrated in Fig. 2, the lower side portions of the arms 32 and 33 are threaded so that they may 2 removably engage the member 25, and are set at such an angle, relative to each other, that only one of the arms may engage the member 25 at a given time. Extending, upwardly from the body 30 of the forked member 29 is a, third arm M, in they end of which is a spring-pressed detent 35 adapted to ride smoothly over the rod 35. Located in abutting relation on either side of the arm 3 and secured" to the rod 35 are the collars 31 and. 38. It will thus be seen that longitudinal motion of the forked member 29" imparts corresponding longitudinal motion to the rod 36.. The rod 36 is mounted for sliding. movement in bearings located in brackets 51" and" 21. The unconfined end of the rod 36' is, coupled to an arm 39 (Fig. 3), securely fastened to the Bucky diaphragm 4B- which is reciprocated beneath an X ray tube 4 I.

The angles at which the arms 32-, 33' and 34 projectfrom the body 30 of the forked member 29, are such that when the detent 35 lies on one side of the rod 36 the threaded portion of the arm 32 engages the threaded portion 25a of the member 25; and when detent '35 lies on the other side of the rod 35 the threaded portion of, the arm 33 engages the threaded portion 25b of member 25 as shown in Fig. 2. Longitudinal motion is imparted to the forked member 29 by virtue of the threaded engagement of either of the arms. 32 or 33, with the rotating member 25; the detent 35 imparting a counterforce preventing the arm from disengaging itself, from the rotating member 25.

On either end of the rotating member 25 are the disc cams 42 and 43. The peripheral surface of each of the said cams is circular except for one lobe as shown in Fig. 1.

Two cam followers 44 and 45 are located in such a position on arms 32 and 33 respectively, that when the forked member 29, advancing towards the cam 42 or the cam 43 by virtue of the rotation of the member 25, reaches either one of the cams, the cam engages its respective cam follower, quickly disengages one threaded arm from the member 25, snaps the detent 35 across the rod 36, and engages with the member 25 the threaded arm that was previously disengaged.

Thus, the reciprocating mechanism may be seen to operate as follows:

The motor 20 rotates the double-threaded member 25 at a constant speed. When the threaded portion of the arm 32 is engaged with the threaded portion 25a of member 25, forked member 29 is caused to travel in a longitudinal direction toward the cam 42. In so traveling the forked member slides over the rod 28 and by virtue of its connection to the rod 36 through the arm 34 and the collars 31 and 38 causes the rod 36 to travel in a like direction. The rod 39 through its connection with the arm 39, which is in turn connected with a Bucky diaphragm 49, causes a longitudinal motion of the said grid. When the arm 32 reache the cam 42, the said cam engages the cam follower 44 and instantaneously disengages the arm 32 from the member 25, snaps the detent 35 to the opposite side of rod 36 and in turn engages the threaded portion of the arm 33 with the threaded portion 25b of the member 25. The last-mentioned engagement produces almost instantaneous reversal of the motion of the forked member 29 and causes the said member to travel in a longitudinal direction toward the cam 43.

In one embodiment this reversal occurred, in less than one-fourth of one percent of the time needed for one complete grid cycle. The forked member 29 through its connection with the rod 39 and the arm 39 causes a similar reversal of travel of the Bucky diaphragm 40. When the arm 33 of the forked member 29 reaches the cam 43 the follower 45 is engaged by the cam 43 which causes disengagement of the arm 33 from the threaded portion 25b and reengagement of the arm 32 with the threaded portion 25a of the member 25. This produces another reversal in travel and causes the forked member 29 to travel in its original direction. Thus, the forked member 29 and thereby the Potter-Bucky grid 40 to which it is attached travel uniformly in a to-and-fro direction, reversal of travel being effected by the disengagement of one of the arms 32 or 33 through the engagement of the respective cams 42 or 43 with the respective cam followers 44 or 45 and the subsequent engagement of the opposite arm.

A box 50 surrounds the reciprocating mechanism and may be filled with lubricating oil through a removable end plate to lubricate the device.

From a consideration of the embodiment of this invention that has been specifically described, it will be appreciated that a simple and effective means has been provided for reciprocating a Bucky diaphragm at the speed required to avoid shadows of the diaphragm appearing on the radiograph. Positive drive in both directions and reversal well within the limited permissible time are insured by the cam means employed to reverse the travel in either direction.

It will be apparent to those skilled in the art that various changes and modifications can be made in the apparatus of the disclosed invention without departing from the spirit and scope thereof as defined in the appended claims.

What is claimed is:

1. In an apparatus for positively reciprocating a Bucky diaphragm, the combination of a rotatable shaft provlded with oppositely threaded portions, and a cam connected to either end thereof, an oscillatable forked member adapted to be connected to a Bucky diaphragm, said forked member being provided with two arms having cam followers projecting therefrom, said arms being spaced longitudinally of said rotatable member and disposed on opposite sides of said rotatable member for alternate threaded engagement with the oppositely threaded portions thereof, and means to oscillate said forked member being adapted to oscillate upon contact of said cam followers with said cams to place the arms thereof alternately in threaded engagement with said rotatable member.

2. An apparatus for reciprocating a Bucky diaphragm at a uniform speed with quick reversal at each end of the stroke comprising a rotatable shaft provided with oppositely threaded portions, an oscillatable forked member adapted to be connected to a Bucky diaphragm, said forked member being provided with arms having cam followers projecting therefrom, said arms being disposed on opposite sides of said rotatable member for alternate engagement with the oppositely threaded portions of said threaded member thereof, and earns secured to said rotatable shaft and rotatable therewith adapted to engage said cam followers for oscillating said forked member to place the arms thereof in threaded engagement with said rotatable member.

RUSSELL H. MORGAN. PAUL C. HODGES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

